Processes for preparing an ethylamine by reacting ethanol with ammonia, a primary amine or a secondary amine are known to those skilled in the art from the literature, e.g. Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, 2000 electronic release, ‘aliphatic Amines: Production from alcohols’.
The ethanol used can be prepared synthetically, for example by hydration of ethylene. An alternative to synthetic ethanol is biologically or biochemically produced ethanol, in particular ethanol produced by fermentation, known as bioethanol. This is prepared from renewable resources and is thus advantageous for ecological reasons. In addition, bioethanol is sometimes cheaper than synthetic ethanol.
However, when bioethanol was used over many amination catalysts, the catalyst deactivation was found to be significantly more rapid than was known in the use of synthetic ethanol.
As a result of the more rapid deactivation, the synthesis has to be interrupted more frequently in order to replace the catalyst. This leads to downtimes, increased costs for the catalyst and change in the catalyst and an increased personnel requirement combined with an increased accident risk.
If bioethanol is used in amination processes, the catalytically active metal surface of the respective heterogeneous catalyst becomes, as has been recognized according to the invention, coated to an increasing extent over time with the sulfur or sulfur compounds introduced via the bioalcohol. This leads to accelerated catalyst deactivation and thus to a significant deterioration in the economic viability of the respective process.
Synthetic ethanol generally has a content of sulfur and/or sulfur-comprising compounds of ≦0.1 ppm by weight (calculated as S), e.g. determined by the Wickbold method (DIN EN 41).
The WO patent application having the application number PCT/EP/04/014591 of Dec. 22, 2004 (BASF AG) relates to a process for reducing the concentration of sulfur and/or a sulfur-comprising compound in a biochemically prepared organic compound, in which the respective organic compound is brought into contact with an adsorbent.
The WO patent application having the application number PCT/EP/04/014588 of Dec. 22, 2004 (BASF AG) relates to a process for preparing an ethylamine by reacting ethanol with ammonia, a primary amine or a secondary amine in the presence of hydrogen and a heterogeneous catalyst, in which a biochemically prepared ethanol (bioethanol) in which the concentration of sulfur and/or sulfur-comprising compounds has been reduced beforehand by bringing it into contact with an adsorbent is used.